Ib Jørgen Melchior (September 17, 1917 – March 14, 2015) was a novelist, short-story writer, film producer, film director, and screenwriter of low-budget American science fiction movies, most of them released by American International Pictures. He was born in Copenhagen, Denmark.

Melchior's novels include Code Name: Grand Guignol, Eva, The Haigerloch Project, The Marcus Device, Order of Battle: Hitler's Werewolves, Sleeper Agent, The Tombstone Cipher and The Watchdogs of Abaddon.

His non-fiction includes the books Quest: Searching for Germany's Nazi Past (with co-author Frank Brandenburg) and Lauritz Melchior: The Golden Years of Bayreuth, the latter a biography of his father, the opera singer and movie star Lauritz Melchior. In 1993 Melchior published an account of his career as a staff sergeant with the US Counterintelligence Corps during World War II, Case by Case: A U.S. Army Counterintelligence Agent in World War II.[3] With his wife, L.A. architect Cleo Baldon, Ib Melchior wrote the non-fiction books Reflections on the Pool: California Designs for Swimming and Steps & Stairways.

Melchior also wrote Hour of Vengeance, a play based on the Viking story of Amled that also inspired William Shakespeare's play Hamlet. In 1982, it was awarded the Hamlet Award for best playwriting by the Shakespeare Society of America.[citation needed]

He claimed to be the creator of the original idea upon which Irwin Allen based his television series Lost in Space, although he never received onscreen credit for this. In 1960, Melchior had created an outline for a series he called "Space Family Robinson", which later became a Gold Key comic book. Ed Shifres' book Lost in Space: The True Story is a detailed documentation of how Irwin Allen allegedly plagiarized Melchior's script, with the two outlines presented side by side.

Decades later, Prelude Pictures hired Melchior as a consultant on its Lost in Space feature film adaptation, but later sold his contract to New Line Cinema, its production partner on the film. New Line agreed to pay Melchior a $75,000 production bonus and $15,000, but refused him his contractually promised two percent of the producer's gross receipts from the film.[5]